1. Field of the Invention
The invention relates in general to a detecting module, and more particularly to a pixel array substrate and a detecting module used for detecting a light signal.
2. Description of the Related Art
Conventional X-ray detection technique which requires the developing of a negative film has gradually been replaced with digitalized X-ray detector. The X-ray detector is composed of a plurality of photodiode arrays formed mainly by amorphous silicon. When the light source of the X-ray detector emits an X-ray of a specific wavelength, the X-ray, first of all, is converted into a visible light by a scintillator. Next, after receiving the visible light, the photodiode arrays generate an electron-hole pair which is collected by the electrode to generate an electrical signal.
In general, the amorphous silicon photodiode arrays form a vertical multi-layer stacking structure, which mainly includes a lower electrode layer, an N-type semiconductor layer, an intrinsic amorphous silicon layer, a P-type semiconductor layer, a transparent conductive layer and an upper electrode layer. The N-type semiconductor layer and P-type semiconductor layer are for increasing the energy barrier of the intrinsic amorphous silicon layer to avoid the leakage current generating an erroneous signal. The N-type semiconductor layer and the P-type semiconductor layer also make the I-V curve of the detector become a diode characteristic curve. Since each film layer requires a lithography process and the thin-film transistor originally has six processes, conventional X-ray detector totally requires more than 11 processes which are too complicated for large scale production. In addition, the larger the required number of layers, the more difficult the manufacturing of film layers, and the lower the yield rate. Since conventionally the photodiode array and the thin-film transistor are manufactured separately and the patterned area of the pixel is limitary, the aperture rate at most is about 70%.